The present invention relates to the measurement of electrical parameters and, in particular, to a probe system for connecting to a device under test.
It is often necessary to make both DC and AC measurements on a device under test (DUT). Precision DC measurements often employ a signal conductor and “guard” conductor located in close proximity thereto. The electronics in the measurement apparatus impresses a virtual version of whatever voltage is on the signal conductor onto the guard conductor so there is no potential difference between the two, thus minimizing effects such as leakage capacitance that can limit low current measurements. AC measurements (e.g., RF, pulse or other signals containing signals having wavelengths comparable to conductor lengths) typically employ a signal conductor and a closely related ground conductor that helps provide the desired bandwidth for AC signals (e.g., coaxial cable or other transmission lines).